1. People always jump to the idea that it'd look silly. Yeah, something like Wolverine's costume could look silly. But when it's designed by professionals and lit right, etc... it'd be perfect. They wouldn't go through with it unless they had a version of it that worked.

2. People cry about the yellow, and I grant you that yellow is a bit much. The brown makes more sense. But I figure that if he's just got blood all over his yellow duds because he's badass and sliced a lot of people up.... you're not gonna care what color it is.

3. People talk about the lack of identity on why he doesn't need the mask, and I have to disagree. He doesn't have a detailed civilian identity to protect, true, but in general, it's preferable not to be immediately recognized by cops and such when you're an outlaw vigilante. Ignore the inherent silliness that his hair would still give him away. If he's running around with a band of mutant outlaws, covering his face makes perfect sense. The movies have goofed it making that level of sense because he didn't do it from the beginning but a story reason can be invented easily. The only real goof is the REST of the X-Men not wearing masks.

4. It's his comic book look. He should have had it from the beginning anyway, reasoning be-damned. It's part of his iconography. Why does Magneto have a cape? That makes as little sense (actually less) than Wolverine having a mask. As I said, Wolvie having a mask can make him anonymous to law enforcement officials. Magneto doesn't use his cape to fly or anything like that. And yet he had his cape.